1. Field of the Invention
The present invention relates generally to data storage, and more specifically, to a system for identifying and managing a plurality of physical volumes, as well as the information stored thereon, in an information storage system.
2. Related Art
The data processing industry stores large amounts of digital data on magnetic tapes, magnetic disks, optical disks, semiconductor memories, and the like. These devices, generally referred to herein as physical volumes, may be implemented for example in the form of cassettes, cartridges, disk packs, or memory modules. The 3480 tape cartridge (developed by IBM Corporation, Armonk, N.Y.) is an example of an industry standard for magnetic storage media. The 3480 cartridge is a single-reel cartridge which houses a length of one-half inch wide magnetic tape.
Conventionally, a pre-printed label adhered directly to the physical volume has been used to identify the volume. Variable alpha-numerical sequences such as serial or identification numbers are used to distinguish a plurality of physical volumes. Machine-readable variable patterns such as bar codes on the labels are used for the same purpose.
Because the data stored in each physical volume is changeable, it is desirable to keep a record of its contents. Such records are frequently maintained in a computer system. Whenever specific information about the physical volume or the data stored therein is required, manual or automated apparatus "read" the identification label and feed this information to the computer system. The computer system then matches a stored data record with the physical volume.
The StorageTek Model 4410 Automated Cartridge System (ACS), available from Storage Technology Corporation, Louisville, Colo., uses such a process. The ACS includes automated apparatus to read identification labels on tape cartridges. The identification labels include a bar coded identification number. A look-up table in a host computer provides a cross-reference between the identification number and information pertaining to the contents of the tape cartridge.
In recent years, this look-up table approach has been complicated by the need to make data accessible to more than a single computer system. This may occur, for example, when a volume is shipped to another geographic location or the media drive is part of a network of multiple central processors. In these circumstances, the traditional, single look-up table is not practical. Further, using multiple, distributed look-tables would also be untenable in the dynamic environment of data storage where table coherency would be essential. Manual handling of physical volumes further complicates the task of data management since the physical volumes and associated data can experience even greater, untraceable manipulations through human intervention.
It is desirable to keep a summary of the contents of each physical volume attached directly to the physical volume. This will allow the identification data to be read and updated at any stage of handling and use. In the case of data cartridges, this has been done in the past by writing a summary in digital form on the medium in the cartridge. However, in order to access this summary, the tape cartridge must be loaded into a tape drive and the tape searched for the summary data. This is a time consuming process, especially when a number of tapes are searched for specific data.
It is desirable to improve the integrity and efficiency of the present physical volume and data management systems.